The present invention relates to an ultrasonic imaging (video) apparatus for transmitting ultrasonic waves to a diagnostic region in an object to be inspected and receiving reflected echoes to obtain and display an ultrasonic tomographic image and a Doppler image of the diagnostic region and more particularly, to an ultrasonic imaging apparatus of adaptive imaging type which can automatically make focus on a moving reflection region desired to be really inspected (ROI region) by monitoring signals indicative of movement and flow in an ultrasonic beam and adaptively making receiving signals developing at the depth (distance between a probe and the signal reflector) be in phase and which can display an adaptive image targeted to only the moving reflection region (moving target) on substantially real time base.
In a conventional ultrasonic imaging apparatus of adaptive imaging type, an ultrasonic beam is formed by electronically controlling circuit characteristics such that phases of transmission/reception signals from/to an array of fine ultrasonic transducers are referenced to a reflected echo signal of high intensity from a living body and reflected echo signal waveforms received by neighboring transducers in the array are made to be in phase and the ultrasonic beam is scanned to image the distribution of acoustic impedances due to structures in the body, the distribution of flow speeds of humors or movements of internal organ or the temporal changes of these quantities.
In the above conventional adaptive imaging type ultrasonic imaging apparatus, however, the ultrasonic image to be displayed is handled in a general manner and adaptive imaging is carried out by correcting phase data without discriminating which region the image belongs to. In this case, since in the ultrasonic image a reflected echo signal from a diagnostic region has, in general, its intensity which is often medium or rather low, focusing cannot be made on a region desired to be observed by an inspector, especially a moving region of interest (ROI) (moving reflection region). Accordingly, focusing is not made on movement of the diagnostic region or a flowing ROI region and its image becomes blurred, thereby failing to provide an excellent diagnostic image.
Accordingly, an object of the present invention is to provide an ultrasonic imaging apparatus which can deal with the problems as above and which can automatically make focus on a ROI region (moving reflection region) desired to be really inspected by monitoring signals indicative of movement and flow in an ultrasonic beam and adaptively making receiving signals developing at the depth be in phase.
Another object of the invention is to provide an ultrasonic imaging apparatus which can display an adaptive image targeted to only the moving reflection region on substantially real time base.
To accomplish the above objects, an ultrasonic imaging apparatus according to the present invention comprises a unit for transmitting ultrasonic beams in a predetermined direction having a moving internal organ in an object to be inspected or blood flow, a unit for receiving reflected echo signals affected by the Doppler effect due to the moving internal organ or blood flow and a unit for detecting a region in which the moving internal organ or blood flow exists from the received reflected echo signals, and image the distribution of irregularities of acoustic characteristics due to body tissues in the object to be inspected and the moving internal organ or blood flow as ultrasonic images, wherein the reflected echo signals from the region in the object to be inspected where the presence of the moving internal organ or blood flow is detected are used to compensate irregularities of acoustic characteristics of body tissues in the object to be inspected so that delay data for adaptive imaging necessary to make ultrasonic waves be in phase at the detection region at adjacent transducers on an ultrasonic probe may be determined, and the ultrasonic transmission/reception is carried out by using the thus determined delay data to perform adaptive image processing.
The delay data for adaptive imaging may be determined in respect of an ultrasonic beam for a given location and immediately after transmission/reception of the above ultrasonic beam, the ultrasonic transmission/reception for the same location may be effected in the same beam direction by using the thus determined delay data.
In this case, the frame rate is decreased by performing the adaptive process but a substantially accurate adaptive process can be effected for the beam.
Further, the delay data for adaptive imaging may be determined in respect of an ultrasonic beams for a given location and the ultrasonic transmission/reception may be effected for a location adjacent to the ultrasonic beam or in the adjacent beam direction by using the thus determined delay data.
In this case, there results an approximate accuracy because the process is not for the same beam but the process can be performed without degrading the frame rate.
Furthermore, the delay data for adaptive imaging may be determined in respect of all ultrasonic beams in a given frame and the ultrasonic transmission/reception may be carried out in the overall beam directions in the next frame by using the thus determined delay data.
In this case, the adaptive process is reflected every frame but each frame can be formed within the same time as that for an instance devoid of the process and therefore a similar image can be formed for movement of the object to be inspected.
Further, the delay data for adaptive imaging may be determined in respect of all ultrasonic beams in a given frame, the thus determined delay data for all ultrasonic beams may be stored together with corresponding ultrasonic beam waveforms by making correspondence of the delay data with the ultrasonic beam waveforms and the beams may be formed by adding the corresponding ultrasonic beam waveforms while compensating them for delay by using the stored delay data.
In this case, the circuit scale is increased but a really accurate adaptive process can be carried out without degrading the frame rate.
Further, in an ultrasonic imaging apparatus relevant to the above invention comprising a probe having an array of a plurality of transducers and being operative to transmit/receive ultrasonic waves to/from an object to be inspected, an ultrasonic circuit unit for supplying transmitting pulses to the probe to generate ultrasonic beams, adding reflected echo signals received by the probe while making them be in phase, processing a beamformed echo signal to deliver it as a tomographic image signal and detecting and delivering a Doppler signal by removing a fundamental wave from the beamformed echo signal through a filter, a phase controller for correcting the reflected echo signals in the ultrasonic circuit unit such that echo signals of neighboring channels are made to be in phase, a digital scan converter unit for performing scan conversion by writing and reading the reflected echo signals from the ultrasonic circuit unit to and from a memory and an image display unit for displaying image data from the digital scan converter unit as an ultrasonic image, there are provided a unit for setting a threshold value of detection level for the Doppler signal in the ultrasonic circuit unit, a unit for extracting a time at which the Doppler signal exceeds the set detection level and a signal level in excess of the set detection level, and a unit for determining, in said phase controller, a ROI depth range for correction necessary to make echo signals of adjacent channels be in phase by using the extracted time and signal level, whereby the focal point can follow the ROI region in the object to be inspected by correcting echo signals from the region where the intensity of the Doppler signal reaches the detection level or its neighboring region so as to make them be in phase between adjacent transducers.
Besides, there is provided a unit for fetching a signal from the unit for determining the ROI depth range and generating a signal for displaying a marker at a position corresponding to the depth range on the image display unit, whereby the marker is displayed at the ROI region in the object to be inspected which the focal point follows.
FIG. 1 is an explanatory diagram showing an outline of operation when the ultrasonic imaging apparatus having the above individual units is applied to a convex scanning format. In FIG. 1, given that a contour 37 of an internal organ exists within a range of frame of a convex scanning area 36 and a blood vessel 38 is inside the contour, it is assumed that an ultrasonic beam 39 passes through the contour 37 of internal organ and the blood vessel 38 at a moment. On the assumption that the contour 37 of internal organ and blood vessel 38 move at the next moment as shown at reference numerals 37xe2x80x2 and 38xe2x80x2, a Doppler shift signal due to the movement is detected and adaptive focusing processing is applied to reflected echo signals from a neighboring structure (wall of the internal organ or wall of the blood vessel) on the basis of the detected Doppler shift signal. This is a feature of the present invention.
Besides, FIG. 2 is an explanatory diagram showing an outline of operation when the ultrasonic imaging apparatus having the above individual units is applied to a linear scanning format. In FIG. 2, it is assumed that a front wall 42 of a blood vessel 41 is within a range of frame of a linear scanning area 40 and a blood flow 43 passes through the blood vessel. It is then assumed that an ultrasonic beam 44 passes through the front wall 42 of blood vessel 41 and the blood flow 43. In this state, a Doppler shift signal generated from the blood flow 43 is detected and adaptive focusing processing (adaptive image process) is applied to reflected echo signals from its neighboring structure (the aforementioned blood vessel wall) on the basis of the detected Doppler shift signal. This is another feature of the present invention.